Time-limit relay



Feb. 11, 1930. E. SCHNETZLER TIME LIMIT RELAY Filed May 5, 1926 00...... 00.00.000.000. %0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0. 000.000.0000....00000. ....0.0..00.00..0..... ...0.0000 0 0 ....0.0 0.000 0 0 0 .0000.00. 0 0 H 0) 0 O ODQDODQDO Q$QPOPO O QQ Patented Feb. 11, 193- UNITED STATES PATENT OFFICE EBERETARD SCHNETZLEB, OF HANAU-ON -THE-MAI1\T, GERMANY, ASSIGNOR TO AKTIEN- GESELLSCHAIFT BROWN BOVERI & GIIEL, OF BAIDEN, SWITZERLAND, A JOINT-STOCK COMP-AN Y TIME-LIMIT RELAY Application filed May 5, 1926, Serial No. 106,994, and in Germany May 18, 1925.

This invention relates to electrical control apparatus, particularly to a type of relay such as is shown and described in patents to Aichele Nos. 1,284,849 of November 12, 1918, and 1,301,991 of April 29, 1919, and which is designed to be operated upon a predetermined variation in current in the controlled circuit.

The general object is to provide a relay device which operates with a controlled time lag between the instant of current change and the instant of tripping.

Another object is the provision of a device wherein the duration of the time lag is susceptible of selective variation.

A particular object is the provision of such a device wherein the lag period may be controlled very accurately and with certainty.

Other objects and advantages will be pointed out or indicated hereinafter or obvious to one skilled in the art upon an understanding of the invention from the present disclosures.

In the drawing forming a part of this specification I show one form of apparatus embodyingthe invention and various modified details, but it is to be understood that these are presented for illustrative purpose only and are not to be accorded any interpretation limiting the invention short of the true and most comprehensive scope of the claims.

In the drawing,

Fig. 1 is a diagrammatic illustration of a relay shown in elevation with the energizing coil in section.

Fig. 2 is a detail showing a modified arrangement for control of the amplitude of vibration of the lag-determining armature, and

Figs. 3 and 4 are details showing modified arrangements of said armature.

The accuracy of the usual types of the time limit relay is not very fine and seldom is less than second. Electric power systems are frequently protected by graded time limit relays and, in view of the above, the tripping time of the last relay to operate is often greater than may be desirable for the safety of the plant.

With the time limit relays constructed according to the present invention the accuracy of adjustment is greatly increased, it being possible to obtain a discrimination of one current cycle, e. g. of 1/25th of a second on a 25 cycle supply. .This is accomplished by the use of a vibrating armature for operating the time limit mechanism, the natural period of vibration of the armature being either equal to or greater than the period of the A. C. supplying the relay. It is of advantage that both the vibrating armature operating the time limit mechanism and a second armature for opening or closing the contacts or tripping the switch are contained in the same magnetic circuit of the relay.

An example of the application of the invention is shown in the drawing representing a relay which starts to operate when an overload partially lifts the main armature. It has been assumed that the components of the time limit mechanism lie in front of the bearing plate m, and are therefore shown in full lines. The tripping gear is assumed to lie behind this plate, and is shown dotted.

This new relay diifers from the previous known types in the presence of the vibrating armature cl connected with the time limit mechanism and lying in the magnetic circuit of the core a. This armature vibrates about the axis 6 in time with the periodicity of the alternating current flowing in the coil 0, keeping within the limits indicated by the full line and dotted positions. The spring f tends to swing the armature cZ out of the core and increase the air gap, while the magnetic attraction tends to draw the armature to the 1 full line position and close the air gap. Two screws 9 limit the amplitude of the vibration. To the armature is attached a pawl k which engages with the teeth of wheel 1L and is maintained in contact by the spring n. A second spring 2' prevents backward motion of the ratchet wheel h.

The armature cl, the spring f, and the pawl is form a vibrating system whose natural period ofvibration must be equal to or higher than the period of the A. C. supply. Since the armature is attracted once every half period of the current it will make a complete vibration fifty times in a 7 second on a 25 cycle supply. At each forward swing the ratchet wheel h is advanced by a certain amount depending on the stroke of the pawl k which may be adjusted by the screws 9. If the adjustment is such that the pawl can only move over a distance of one tooth pitch, then 50 teeth will be advanced in one second; if the ratchet wheel has 50 teeth it will therefore make one revolution per second. If the stroke of la exceeds one tooth pitch, the speed of It will be correspondingly higher.

A pinion 0 is fixed with. ratchet wheel h on the supporting pin :0 journaled in plate m, and is caused to engage with the toothed quadrant p pivotally IIIOlIltEd on the pin y carried by the lower free end of a lever u, when the tripping armature b is partially raised, the release lever 8 being held by a catch 2? also pivotally mounted on pin 3 so that the quadrant is swung toward the pinion 0 against the spring r. Lever u is pivotally mounted on a pin .2 fixed in plate m. The quadrant carries a pin 9. When the quadrant p reaches the end of its travel, (the position shown in the drawing) this pin 9 lifts the catch t, pivotally mounted on the free end of lever u, from the point of lever 8, thus allowing the armature b to be fully raised and take up the position in which it is shown. in the drawing.

The lever s is pivotally mounted, with armature b, on the pin a for relative move ment with respect to the armature, and. is provided with the portion 12 disposed for seating engagement with extension 0 of-the armature to limit counter-clockwisepivotal movement of lever s with respectto the armature, due to the action of the tension spring d. The catch t is provided with the portion or extension 6 disposed for engagement with the lower free end of lever u to limit clockwise pivotal movement of the catch in such wise that the same will always drop, upon being released, to the position shown, to insure for relatching engagement of the same with the upper end of lever 8 upon counterclockwise, resetting'movement of the latter with armature b.

The armature extension 0', as shown, cooperates with the usual rod Z for tripping a circuit breaker (not shown).

The operation is as follows, assuming that the circuit breaker referred to is closed and armature b in open position, at which time the upper end of lever s is in latching relation with catch t, and quadrant p in its lowermost position and out of meshing engagement with pinion 0. In the case of a moderate excess current, armature b is attracted and moves upwardly, at which time lever s is moved in a clockwise direction on account of its connection with the armature by spring d. 'Such movement of lever 8 causes counter-clockwise movement of lever it against the action of spring '7' to move quadrant p to the right into meshing engagement with pinion 0. The armature d, which is now vibrating, operates as explained above, to rotate pinion 0. whereby quadrant p is caused to rotate in a counter-clockwise direction about pin 3 until the pin 9 engages catch t to lift the same out of latching relation with respect to lever s, at which time armature b is released and permitted to complete its closinn; movement and move to the position shown, thereby operating through rod f to release the circuit breaker. Simultaneous with this action, spring r operates to move lever u back to the left to its initial position, thereby moving quadrant 37 also to the left out of meshing relation with pinion 0, quadrant p and the catch '2. then dropping by their own weight to their initial positions. After coil 0 becomes deenergized, due to the tripping of the circuit breaker, armature 6 also drops to its initial position, causing relatching engagement of lever s with catch t.

If the moderate excess current ceases before the toothed sector or quadrant p has been driven or raised by the time mechanism into the tripping position, whereat pin 9 engages catch 25 to release the same, as explained above, armature b, lever s, catch 2? and lever to assume their previous normal positions under the action of spring 1", at which time quadrant p is also moved to its initial lefthand position out of meshing relation with pinion 0, and accordingly drops under the action of gravity to its normal position.

In the operation of the present embodiment of the invention, during occurrences of a moderate excess current, spring cl does not come into action as a spring, the mechanism operating as though lever s were integral or made in one piece with armature extension 0'.

In the case of high excess current, the attractive force of the electrom'agnet is so great as to attract and draw armature b immediately upwardly into its end or closed position in which it is shown in Fig. 1. At such time,

.quadrant 72 is moved into meshing relation with pinion 0, in the manner explained hereinabove, the spring (2', however, stretching and the portion bof lever 8 being lifted clear from its seating surface on armature extension 0 on account of the occurring rela- I tive clockwise movement of armature b with 'respect to lever s, as will be apparent. Upon occurrence of high excess currents, therefore, the circuit breaker is tripped immediately and independently of the timing mechanism. The lag period may be lengthened or shortened by the shortening or lengthening of the stroke ofarmature '03 through adjustment of screws 9, whereby the speed of feed of ratchet h is varied.

In certain circumstances it may be of advantage to make the amplitude of vibration of the vibrating armature somewhat greater than the stroke required. This is very easily accomplished by providing the pawl 70 with a slot '0.

As will be seen, the tripping time of the relay is dependent on the periodicity of the alternating supply and not on the strength of the current. 11 it is desired to malze the time dependent on currentas well, this can be done by providing the stops 9 with springs as shown in Fig.2. The amplitude of the armature vibrations. will then increase with the current, giving a longer stroke to the pawl 70 and consequently a shorter time lag.

The invention is not limited to the form shown in Fig. 1; for example, the shape of the vibrating armature may be modified as illustrated in Figs. 3 and 4.

What I claim is:

1. An electrical relay comprising, in combination, an electromagnet, a tripping armature operable thereby, a vibrating armature operable by said magnet, progressively actuated means operable by the vibrating arma ture, and a detent controlling said tripping armature and being operable by said progressively actuated means.

2. An electrical relay comprising in combination, an electromagnet, a tripping armature operable thereby, a vibrating armature operable by said magnet, means operable by said vibrating armature for controlling said tripping armature, and means for varying the amplitude of vibration of the vibrating armature.

able by the vibrating armature upon energiza-' tion of said magnet for a predetermined period. V

4. The combination with a relay including an electromagnet, a tripping armature operable thereby, and means for control ing operating movement of said armature, or" means supported and disposed for reciprocatory.

movement under the influence of said electromagnet and'cooperable with said controlling means upon such movement to efiect actuation of the latter. v v

5. The combination with a relay including an electromagnet, a tripping armature operable thereby, and means for controlling operating movement of said armature, of means for actuatingsaidcontrolling means and including a ratchet wheel, a pawl supported for reciprocatory movement and cooperable with said wheel upon such movement to effect rotation thereof, and means operable under the influence of said electromagnet for imparting such movement to said pawl.

65. in a relay, an electromagnet comprising a core and an exciting coil therefor, a tripping armature associated with said core, means for controlling tripping movement of said armature, and means for actuating said controlling means, said actuating means including a ratchet wheel, a pawl supported for reciprocatory movement and cooperable with said wheel upon such movement to impart rotary movement thereto, and means responsive to conditions of excitation of said coil for ellecting such movement or said pawl.

7. In a relay, an electromagnet comprising a core having an air gap and an exciting coil for said core, a. tripping armature associated with said core, means for controlling tripping movement or" said armature, a second armature, spring means cooperating with said second armature, said second armature being disposed in said gap and forming part of said core and being supported for vibratory movement consequent upon excitation of said coil and by virtue of the action of said spring means, and means for actuating said'controlling means, said actuating means being cooperable with and operable upon such movement of said second armature.

S. in electrical relay apparatus, an electro magnet, an armature operable thereby, means operable to control operating movement of said armature, and means forming part of said control means and being supported for operating vibratory movement at a period corresponding to the frequency of an energizing alternating-current supply for said electromagnet.

In testimony whereof l have hereunto subscribed my name at Frankfort-on-the-lviain, Germany, on the 5th day of March, A. 1926.

EBERHARD SCHNETZLEE. 

